Method of annealing



May 12, 1936. R. J. WEAN y METHOD oF ANNEALING Filed' pct, 15, 1935 2 Sheets-Shadi. 1

INVENTOR Y Patented May 12, 1936 UNITED STATES PATENT OFFICE METHOD F ANNEALING Raymond J. Wean, Warren, Ohio Application October 15, 1935, Serial No. 45,083

2 Claims.

'I'his invention relates to annealing and, in particular, to the annealing of material such as flat rolled steel products, i. e., sheets or strip in coils, although it has other applications. v

5 'Ihe first step in the improvement of the art of annealing by the aid of the conventional annealing boxes which were charged bodily into annealing furnaces, was the development of a so-called bell or cover type furnace adapted to be lowered over a charge of material supported on a suitable base. The cover type furnace performs the same function as the annealing box cover, i. e., excludes the atmosphere to prevent oxidation of the material, and also furnishes the heat necessary for annealing. In order to prevent oxidation of the material upon removal of the cover, it was necessary to cool the furnace and charge to a temperature at which the oxidation would not proceed rapidly enough to be objectionable, viz., about 1000" F. This meant that the furnace had to be kept over the charge for a long period after its heating function had been completed. This imposed serious limitations upon the capacity of a furnace of the bell type.

To overcome this limitation, it was proposed to place inner covers over the charge before lowering the furnace covers thereover. By this expedient, the furnace covers could be removed as soon as the charge had been raised to annealing temperature, and placed over a succeeding charge of material to be annealed, the inner cover being relied on to exclude the atmosphere during the cooling stage of the annealing cycle. Such inner covers are quite costly and havel only a relatively limited life, due to the extreme temperature conditions under which they operate, being subject directly to the furnace temperature during the heating cycle, and then to atmospheric oxidation while cooling.

I have invented a method and apparatus whereby the charge can be protected against atmospheric oxidation at all times without the necessity vof subjecting the inner cover to the severe temperature conditions existing in the heating stage of the cycle. In accordance with my invention,

I employ a furnace of the cover or bell type,

but do not use the inner cover during the heating stage of the annealing cycle. 'I'he charge is brought up to annealing temperature with the furnace cover thereover. The latter is then removed while the charge is at a temperature such that exposure to the atmosphere would result in objectionable oxidation of the material. A shielding cover similar to the inn-er covers now in use is then placed over the charge to protect it from (Cl. 26S-5) the atmosphere. In the interim between the removal of the furnace cover and the lowering of the shielding cover, I protect the charge against oxidation by forming a curtain of non-oxidizing atmosphere on all sides thereof. Since the shield- 5 ing cover is not subject to the furnace temperature during the heating stage of the annealing cycle, and is subject to the heat of the charge only during the cooling stage, the life of the shielding cover is much greater than that of the inner 10 covers heretofore used.

For a more complete understanding of the invention, reference is made to the accompanying drawings illustrating a present preferred embodiment of apparatus for practicing my invention. 15 In the drawings- Figure 1 is a transverse sectional view of a bell type furnace having a charge therein ready to be annealed;

Figure 2 is a plan view of the furnace base 20 which supports the charge and receives the cover;

Figure 3 is a view similar to Figure 1, showing the charge on the base after the furnace cover has been removed and with the shielding cover in the course of being lowered over the charge; and 25 Figure 4 is a similar view showing the shielding cover in its final position.

Referring now in detail to the drawings, av bell type furnace I0 comprises a base II and a cover or bell I2. Both the base and cover have a re- 30 fractory lining assembled within a structural frame. 'I'he furnace is similar in general to that shown in U. S. Patent No. 1,952,402. The joint between the base and cover is closed by a seal I3. A charge I4 of material to be annealed,- in 35 this example, a stack of sheets, is supported on a bottom plate I5. A seal I6 surrounds the charge 1 and is adapted to cooperate with a shielding cover to be described later.

The furnace I 0 may be heated by any suitable 40 means. Since the present invention is not concerned with the specific heating means employed, the latter has not been shown in detail, and may constitute the radiant tubes as shown in the patent aforementioned, or other heating means 45 such as electrical resistors or fuel burners.

A gas supply duct I1 is embedded in the lining of the base II and extends entirely around the bottom plate I5 outside the seal I 6. A plurality 50 of nozzles I8 extend upwardly and inwardly from the ducts I1 at short intervals around the plate I5. Connections I9 extend laterally from the duct I1 to any convenient source of a non-oxidizing gas. This may be natural gas if such is 55 available, or any other suitable non-oxidizing gas.

Having described the apparatus of my invention, I will now explain the method practiced by the aid thereof. The cover I2 of the furnace is first removed from the base II to permit the charge I4 to be disposed thereon in the manner shown. The cover I2 is then replaced and the charge heatedthereby to the annealing temperature. When the proper temperature has been reached, the cover I2 is removed. Substantially simultaneously with the removal of the cover I2 from the heated charge, non-oxidizing gas is supplied to the ducts I'I by operating suitable control valves. The nozzles I8 thus form curtains 20 of non-oxidizing gas on all sides of the charge. If the gas is combustible, it will be ignited on contact with the heated charge if suiiicient air for combustion is present. This will be provided as the cover I2 is raised. So long as the supply of gas to the ducts I1 is continued, the curtains 20 protect the charge from atmospheric oxidation on all sides. The top sheet in the stack may suier some oxidation, but this can be scrapped with but little loss or a special cover sheet can be placed on the top of the stack.

After the heating cover has been removed, a shielding cover 2| is placed over the charge as indicated in Figure 3. The lower edges of the cover 2I cooperate with the seal I6 and the atmosphere is thus effectively excluded from the interior of the cover. When the cover 2I has been lowered to the position shown in Figure 4, the gas supply for the ducts I1 may be cut oif and the charge then permitted to cool in the normal way. The furnace cover, of course, is then lowered over a succeeding charge of material to be annealed and is thus operated with the highest eiiiciency, i. e., substantially continuously, in the performance of its function, viz., the heating of the material to be annealed to the proper annealing temperature.

The advantages of the invention will be apparent from the procedure that has been described. In the first place, the efciency and capacity of the heating cover are not impaired by the necessity for using it as a shield against atmospheric oxidation in addition to its heating function. Secondly, the shielding cover 2l is never subjected to the extreme temperature which exists on the inside of the furnace during the heating cycle and its life is therefore much greater than that of the inner covers as used heretofore. The maximum temperature to which the shielding cover is subjected is that of the fully heated charge, but this does not seriously affect the life of the cover since the charge starts to cool as soon as the heating cover is removed. The method and apparatus of my invention because of the increased life of the shielding covers as compared with that of the inner covers used previously, makes possible a material saving in cost over former practice.

Although I have illustrated and described herein but a preferred practice and embodiment of the invention, it will be apparent that changes therein may be made without departing from ,the spirit ofthe invention or the scope of the appended claims.

I claim:

1. In a. method of annealing, the steps including disposing a charge of material to be annealed on a support, lowering a heating cover thereover to heat the material, removing the cover` while the material is at a temperature such as to cause atmospheric oxidation thereof, discharging nonoxidizing gas adjacent the base of the charge to protect it against such oxidation, and then lowering a shielding cover over the charge to protect it from oxidation while cooling.

2. In a method of annealing, the steps .including disp'osinga charge of material to beannealed on a support, lowering a heating cover thereover to heat the material, removing the cover While the material is at a temperaturel such as to cause f atmospheric oxidation thereof, forming a curtain of non-oxidizing gas around the charge to protect it against such oxidation, and then lowering a shielding cover over the charge to protect it from oxidation while cooling.

' RAYMOND J. WEAN. 

